Diagnostic evaluation of the prostate has been difficult because of it's anatomical location and it's histological characteristics. Furthermore, the lack of contrast material which accumulates in the prostate has hampered objective evaluation of this gland. Rectal digital examination has been the standard means of diagnosis of early carcinoma and for following patients after therapy. This method however is highly subjective often presenting problems of inter institutional comparisons. The advent of computarized tomography has not significantly improved our capabilities of evaluating the prostate with the exception of large tumors with extension outside of the capsule. Recently two new imaging modalities, transrectal ultrasound (TRUS) and magnetic resonance imaging (MRI) have been used to evaluate the prostate. We have in a preliminary fashion evaluated both of these imaging techniques and compared results in response to therapy and with anatomical specimens removed during surgery. In the present application we propose to: 1. Evaluate preoperative TRUS and MRI in patients with localized prostatic cancer undergoing radical prostatectomy and compare results with serial anatonopathological sections of the prostate. 2. Evaluate pre therapy TRUS and MRI in patients with localized prostatic carcinoma undergoing radiation therapy and compare results post therapy. 3. Determine the relationship of local response to therapy to systemic response in an attempt to use volume reduction of the prostate as an objective parameter. 4. To evaluate the role of these new modalities as possible screening of populations at risk of developing prostate carcinoma.